I had the same 830/930 dilemma, while picking the phone.
I went for the 830 bc of better battery, glance, because it was much more comfortable to hold than the 930. 930 also had the heating issues - it got really hot even performing tasks during which you wouldnt think it would. I also didn't wanna risk the display issues and bugs that a lot of users are complaining about. Display wise - yes, 930 has a better, sharper display in comparison, but 830 is more than good enough, its plenty sharp.
If you use the phone for generic tasks such as internet, mail, chatting and stuff like that, you won't basically see a performance difference between both of them. Where the 930 wins is when playing hardcore 3d games and obviously camera and image processing - so if you do a lot of photos, it will handle them quicker.
If you care about battery life, 830 is better (the battery doesn't have to handle such powerful processor and display).